This application seeks funding to take advantage of a unique opportunity provided by a $6 million National Highway Traffic Safety Administration (NHTSA) program to conduct the first-ever case-controlled study of the relative risk of drugged driving. That study will recruit 2,500 crash-involved drivers and 5,000 comparison drivers to participate in roadside interviews that will collect breath tests for BAC and oral fluid and blood samples to identify drug involvement. NHTSA has contracted with PIRE to conduct the drug risk study, providing an opportunity for using it as a framework for adding-on a study of the relative risk of crash involvement of drivers with alcohol use disorders. The proposed add-on would also identify hardcore drinking drivers through their driving records to determine their prevalence in traffic crashes. The add-on study would also provide for the collection and analysis of crash records to determine crash responsibility, which will permit for the first time the calculation of relative risk of causing a crash, rather than simply being involved in a crash. Finally, the add-on study, through the collection of information on alcohol use disorders on the drivers in the NHTSA drug risk study, will permit the determination of the relative risk of drivers with comorbid alcohol and drug use problems. PUBLIC HEALTH RELEVANCE: Public Health Relevance Statement This study is directed at the prevention of the 13,000 fatalities caused by alcohol-related crashes involving impaired drivers each year in the United States. It will determine the prevalence of drivers with alcohol use disorders in traffic crashes and provide information to policymakers concerned with treatment and prevention programs.